Fire alarm



FIG. 1 is a front elevational view of a fire alarm showing my new design;

FIG. 2 is a top plan view thereof, the bottom having the same appearance;

FIG. 3 is a rear elevational view thereof; and

FIG. 4 is a right side elevational view thereof, the left side having the same appearance. 

The ornamental design for a fire alarm, as shown. 